Centrifugal casting machine



MMay 12, 1931.. MFRISTJR v 1,805,168*

ENTRIFUGAL CASTING MACHINE Filed arch 27'. 1929 s sheets-sheet 1 I My 12, 1931. R. P. FRlsT, .JR 3,805,163

GENTRIFUGAL CASTING MACHINE' Filed March 27. 1929 5 Sheets-Sheet 3 Patented May 12, 1931 UNM s'r'r FFI E CENTRIFUGAL CASTNG .MACHINE Application filed March 27,

This invention relates to metallurgy, and more particularly to a machine useful in making metallic and other castings of selfhardening material,

An object of the invention is the provision of an improved type of centrifugal casting machine, wherein iiuid or plastic self-hardening material such asl molten metal, is impelled into a suitable mold by centrifugal "it action, the mold and the container in which the self-hardening material is retained be. fore being impelled into the mold, being mounted for rotary movement, whereby the desired centrifugal force is developed.

Another object is the provision of a centrifugal casting machine wherein both the mold, and an electrically heated Crucible, are mounted upon a'revoluble support, an outlet from the crucible communicating with the Q9 gate of the mold, so that molten material may be impelled from the crucibl-e into the mold by centrifugal force when the supporting means is rotated.

M A more detailed object is the provision of 9 a centrifugal casting machine as described,

wherein the rotatable member is connected 1to the rotating means in such a manner that rotary movement is so suddenly imparted to the supporting means, that the maximum speed of rotation thereof is attained substantially instantaneously.

A further object is the provision of a casting machine as described, having improved means for clamping the mold in posicrucible. f

A still further object is the provision of means for adjusting the mold retaining heads at a point remote from the crucible, to minimize thev danger of the operators being burned.

A still further object is the provision of improved means for supplying the electrical- "55 with electrical energy.

A still further object is the provision of an electrically energized and revolubly mounted crucible as described, having a thermo-couple associated therewith, and

50 means for electrically connecting this movation to receive the molten material from the" ly energized and revolubly mounted Crucible,

1929. Serial No. 350,333.

ble thermo-couple With the stationary indicating gauge adapted to register the temperature of the Crucible and itsl contents.

A still further object is the provision of a casting machine as described, which, while being of general application, is particularly adapted for casting relatively small objects such as jewelry and, more particularly, metallic dental fillings.

A still further object is the provision of the motor-driven centrifugal casting machine having an electrically energized cruci# ble in communication with a suitable mold, and in which the supply of electrical energy to both the driving member and the Crucible, is controlled by a single switch.

A further object is th-e provision of a device of the general class described, which is very simple in operation and construction, and yet, which is capable of operating ethciently to perform the functions desired.

The invention possesses other objects and advantageous features, some of which, with those enumerated, will be set forth in the following description of the inventions particular embodiment which is illustrated in the drawings accompanying and forming a -part of the specification.

Referring to the drawings:

Figure l is a perspective view of a casting machine embodying the principles of my invention.

Fig. 2 is an enlarged, vertical, medial sectional view.

Fig. 3 is a vertical sectional view taken upon the line 3-3 of Fig. 2, with the direction of view as indicated.

Fig. et is a perspective view of the improved form of mold adapted for use with the casting machine of Figs. l and 2.

Fig. 5 is a diagrammatic view of the electrical connections forming a portion of my invention.

I am aware that casting machines have previously been employed, wherein a mold is supported for revolution about an axis spaced therefrom, and wherein means are provided for introducing self-hardening material such as moltcnmetal, into the mold during rotation thereof, by centrifugal acm0 tion. However, to my knowledge, none of these prior casting machines, is capable of imparting rotational movement to the mold so suddenly that full speed is attained thereby substantially instantaneously, as lis the case with the casting machine of the present invention. This improvement is of importance, in that it develops the maximum centrifugal force practically instantly, to impel the molten material into the mold at relatively high velocity. Inasmuch as very small quantities of metal are being handled in the embodiment of the invention, which is designed for making dental fillings, it is desirable to impel the molten material from the crucible into the mold, as rapidly as possible, so as to preclude the possibility of its cooling beyond thoroughly fluid state; otherwise a casting of maximum density will not be attained.

For the purpose of the present disclosure, I have selected an embodiment of my invention, adapted to make very small castings such as gold dental fillings or small pieces of jewelry. This embodiment comprises a base 6 having an electric motor 7 disposed therein with its shaft 8 in vertical position. A hollow supporting arm 9 is journalled upon the top ofthe base 6, for rotary movement in a horizontal plane. For this purpose the arm 9 is supported upon a vertical shaft 11, by means of a fitting 12. The shaft 11 is revolubly mounted in axial alignment with the shaft 8 of the motor 7, upon preferably a pair of anti-friction bearings 13, the inner race 14 of each bearing, being rigid with the shaft 11, and the outer race 16 of each bearing, being rigid with an extension 17 of the base 6. One or both of the antifriction bearings 13, are capable of sustaining the downward thrust of the shaft 11, to support the weight of the arm 9 and parts carried thereby. Rigidly attached to the lower end of the shaft 11, is a flange 18 encircling the upper end of an extension 19 of the motor shaft 8 which is mounted for free rotation inside the flange 18. A convenient method of attaching the flange 18 to the shaft 11, is by a nut 21 threaded to the lower end of the shaft 11, as clearly shown upon., Fig. 2. The shaft 11 is connected to the shaft 8, to be rotated thereby, by any suitable flexible connecting member such as a leather thong 22 connected at one end t0 the flange 18, and at the other end, to a flange 23 carried by the extension 19 and spaced from' the flange 18.

' A head 26 is rigidly attached to the arm 9, adjacent one end thereof, spaced from the aXis 0f rotation of the arm. To the inner face of this head 26, a crucible 27 is rigidly attached. This crucible is adapted to be heated by electrical energy, and is preferably'of the inductance type, being provided with a coil 28 encircling the cavity 29 of the crucible, so that metallic contents of the crucible, are heated by their internal resistance to the eddy currents induced therein when the coil 28 is traversed by a relatively low frequency current. However, it should be understood that 1 contemplate employing any suitable type of electrically heated crucible 27. The coil 28 is supplied with electrical energy, by means of a pair of conductors 31' electrically connected to the opposite ends of the coil 28, as by binding posts 32, and leading to binding posts 33 which are carried by an insulating head 34 in the form of a disc carried by the shaft 11. Each of the binding posts 32 is electrically connected to a contact 36 let into the annular surface of the disc 34, so` that each of the contacts 36` is adapted to be engaged by a contact 37 let into the inner surface of an annular insulating head 38 which is rigidly mounted upon the base 6, by a sleeve 39, andv which encircles the disc 34. Each of the contacts 37 is pressed radially inwards, by a spring 41, and each is electrically connected to a bindinu post 42, their conductors 43 leading from the binding posts 42, to a control switch 44 suitably mounted upon the base 6. Current may be supplied to the switch 44, by conductors 46 leading from any suitable lsource of electrical energy. It is Obvious therefore, that when the switch 44 is turned to the proper position, and when the arm 9 is turned to that position in which each of the contacts 36 is engaged by one of the contacts 37, the coil 28`is energized.

To permit easily ascertaining the temperature of the crucible 27 and its contents, a thermo-couple 51 is suitably associated therewith in such a manner, that the thermo-couple 1s raised to the same temperature as the contents of the crucible 27. This thermo-couple is connected by conductors 52, to binding posts 53 carried by the rotating head 34, each of which is electrically connected toa contact 54. Each of the contacts 54 is adapted to be engaged by a contact 56 which is carried by the stationary annular head 38, and which is urged by a spring 57 radially inwards toward the revoluble head 34. Each contact 56 is electrically connected to a binding post 58; and electric conductors 59 establish electrical connection between the binding posts 58 and a galvanometer 61, the indicating hand 62 of which is adapted to be moved in respect to the indicia 63 of the galvanometer 61, by current induced in the thermo-couple 51, when the temperature thereof is raised. The parts are so proportioned and arranged that the contacts 54 and 56 are in-engagement with each other at the same time as that when the contacts 36 and 37 are in engagement with each other. y

The crucible 27 is provided with an outlet port 66 extending laterally therefrom slightly above the bottom of the cavity 29. This port 66 extends through the outer side of the ciucible, and communicates with an aperture 67 arranged centrally ofthe fixed head 26, the` outer face of which is provided with a plurality of concentric, circular recesses 68. An opposed follower head 69 is carried by a rod 71 slidably mounted Within the hollow arm 9. A set screw 72 or its equivalent, is threaded through the under side of the arm 9, and has its inner end disposed within aslot 73 in the under side of the rod 71, restraining the rod 71 against rotating within the arm 9,

but permitting free longitudinal movement y of the rod in respect to the arm. The end 74 of the rodl 71, opposite the head 69, is provided with a longitudinally extending and internally threaded-bore 76 into which an operating rod 77 is threaded. This rod 77 extends through the end 78 of the arm 9, opposite the fixed head 26, and has a preferably knurled head 79 rigidly secured thereto. The head 79 and operating rod 77 are revoluble in respect to the arm 9, but are held against longitudinal displacement therein by a sleeve 81 held rigid with the arm 9, as by a doWel 82, and engaged by flanges 83 and 84 carried by the rod 77. Y

From this construction it is obvious that by turning the head 79, the threaded rod 77 may be turned within the bore 76 of the iod 71, effecting variation of the distance between the follower head 69 and the fixed head 26. The inner face of the follower head 69 is also provided with a plurality of concentrically" arranged circular recesses 86, these recesses 86 being disposed in alignment with the corresponding recesses 68 in the fixed head 26.

The recesses 68 and 86 are adapted to receive the ends of the flask, or investment ring 87, of the mold, or investment, 88. `This investment is constructed in the conventional manner, by taking a preferably wax impression of the dental cavity to be filled, and then constructing the investment around this impression, by placing the impression within the flask, or investment ring, 87, and then fill-A ing the remainder of the investment ring,

with suitable molding material, leaving a gate 91 leading from the impression to the exterior of the investment at one end thereof. AThe wax impression is then melted out, leaving a cavity 92 within the investment, complementary in shape to the desired filling.

For convenience in forming this investment, the investment ring 87 comprises a flexible band bent to substantially cylindrical formation, the ends 93 thereof, defining a split 94 extending longitudinally of one side of the cylinder. Spaced from both ends of the ring thus formed, and upon opposite sides of the split 94, a fiange 96 is formed. These flanges may be engaged by a clip 97 which is adapted to press the flanges firmly together and hold the investment ring in substantially true, cylindrical form, but to permit separation of the ends thereof, when it is desired to remove the contents. The recesses 86 and 68 are so proportioned that they are adapted to receive opposite ends of an investment so constructed, recesses of different sizes being employed to permit mounting therein, several different sizes of investment. In making the investment, the gate 91 thereof, should be so disposed that it is adapted to be brought into register with the port 66 of the `Crucible 27, when the investment is properly engaged bet-Ween the heads 26 and 69.

A counterbalance 101 is slidably mounted upon the arm 9 upon the opposite side of the fitting 12, from the head 26. A plurality of notches 102 are formed in the arm 9; and a pin 103 extends transversely of, and is slidable Within the counterbalance 101. This pin 103 passes through one edge of the aperture 104 iii the counterbalance 101 through which the arm 9 extends, and is provided with a reduced portion 106, so that by pulling the pin 103 to the right, as viewed upon Fig. 3, this portion may be brought into register with the aperture 104, to permit sliding the couiiterweiglit 101 on the arm 9. This will permit disposing the counterweight 101 in proper position to counterbalance the weight carried by the other end of the arm 9, where'- upon the pin 103 may be engaged with the suitable notch 102, to hold the coiinterweiglit 101 against displacement. A spring 107 under compression between the counterweight 101 and a flange 108 on the pin 103, resiliently retains thepin 103 in locking position.

The motor 7 is adapted to be energized by current carried thereto, by conductors 111 leading from the motor 7 to the switch 44 which is of such a nature that it is adapted to optionally energize the conductors 43 or 111 from the conductors 46, or to deenergize both sets of conduct-ors, depending upon the position of the manually movable knob 112 and indicating hand 113 carried thereby. Means for varying the speed Aof the motor 7, are provided. Preferably this means is iii the form of a lever 116 extending through a slot 117 in the side of the base 6, and adapted to vary the speed of the motor by moving one of the brushes thereof, or by varying the electrical resistance connected in series with the motor.

I will now proceed with a description of the operation of my improved casting machine. ,l

First of all, a suitable investment 88 should be constructed by means of the investment ring 87, the cavity 92 of the investment 88, being complementary in shape to the desired filling. This investment should then be gripped between the follower head 69 and the fixed head 26; and inasmuch as the heads are provided with the recesses 86 and 68 respectively, it will not be necessary to disturb any of the material of which the investment is made, to grip the investment between the heads. This is an improvement over earlier devices in which the heads were provided with projections adapted to seat inside the investment ring, requiring Cutting away a certain amount of the material of which the investment was made before the investment Could be engaged between the heads.

In positioning the investment 88 between the heads 69 and 26, it should be turned so that its gate 91 registers with the outlet port 66 of the Crucible 27.

If desired, the Crucible 27 may be energized to be raising the temperature of the material of which the casting is to be made, during the time that the investment 88 is being adjusted Abetween the heads 69 and 26. This'may be effected without danger of burning the operator, because of the fact that the head 79,/whereby the distance between the heads 69 and 26 is varied, is disposed at the opposite end 78, of the arm 9, from that upon which the Crucible 27 is carried. This feature therefore makes possible a considerable saving of time in the use of the casting machine.

As explained above, before the coil 28 of the Crucible 27 can be supplied with energizing current, the arm 9 must be turned to that position in which the contacts 36 and 54 of the movable head 34, are in engagement with the contacts 37 and 5d respectively, of the stationary head 38. Consequently, the indicating means or galvanometer 61, will show when the material in the Crucible 27 has been heated sufficiently to reduce it to the desired state of plasticity o-r Huidity, since the indicating hand 62 indicates the temperature inside the cruciblc. W hen this temperature has been attained, the lmob 112 of the switch all, should be turned to that position in which current from conductors 46, is transmitted to the motor 7. This 'will eii'ect energization of the motor 7, causing the shaft 8 thereof to revolve. However, the shaft 11 will not be affected until all the slack of the thong 22 has been wrapped upon the extension 19 of the shaft 8, it being understood that before commencement of the heating of the Crucible 27 the arm 9 has been rotated in a reverse direction to wind the thong 22 in a reverse direction upon the extension 19. Consequently, the shaft 8 of the motor 7 will attain full speed of rotation before the shaft 11 is rotated, and when the shaft 11 does startto rotate, it will have rotational movement imparted thereto so suddenly that its maximum speed is attained subst-antlally instantaneously.

impel the contents of the Crucible through the port 66, aperture 67, and gate 91, into the cavity 92 of the investment 88; and this impelling of the fluid contents of the crucible 27, will be at high velocity, assuring that the molten material reaches the cavity 92 practically instantaneously; with the result that it has no opportunity to cool and solidify until it is disposed inside the cavity 92. Here it may cool; and in view of the fact that rclm tation is continued during the cooling process, the Centrifugal force acting thereupon, will compact the material within the Cavity 92 during the entire cooling process, producing a casting of maximum density. After this has been accomplished, the motor 7 should be stopped, and the investment 88 ,removed from between the heads 69 and 26, whereupon it may be broken open and the nished casting removed therefrom.

It is to be understood that the details of the invention as herein disclosed, are subject to alte-ration within the spirit or scope of the appended claims.

I claim:

1. A casting machine comprising an arm, means for suddenly imparting rotation to said arm about an axis spaced from an end thereof and maintaining said rotation at a speed as great as the initial speed of said arm, a Crucible supported upon said arm adjacent said end thereof, a mold, and means for securings l mold to said arm beyond said Crucible from said axis with the gate of the mold in register with an outlet from said Crucible.

2. A casting machine comprising an aim., means supporting said arm for rotation about an axis spaced from an end thereof, a motor, means connecting the arm to said motor to be rotated thereby, said connecting means including a flexible member, whereby movement of said arm is delayed untilsaid motor has rotated for a period of material length, a mold secured to said arm adjacent said end thereof, and means for introducing self-hardening material into said mold during rotation of said arm.

3. A casting machine comprising an arm, means supporting said arm for rotation about an aXis spaced from an end thereof, a motor, means connecting the arm to said motor to be rotated thereby, a head rigid with said arm adjacent said end thereof, a follower head adjustably carried by said arm, said heads having aligned 'recesses therein for the reception of the ends of the mold, means for adjusting the position of said follower head in respect to the rigid head, and means carried by said rigid head for introducing self-hardening material to said mold during rotation of the arm. f

4. A casting machine comprising an arm, means supporting said arm for rotation about an axis spaced from an end thereof, a motor,

lit

asoales means connecting the arm to said motor to be rotated thereby, a head rigid with said arm adjacent said end thereof, a follower head adjustably carried by said arm, said heads having aligned recesses therein for the reception of the ends of the mold, means carried b v said rigid head for introducing molten material into said mold during rotation of said arm, and means remote from said introducing means for adjusting the position of said follower head in respect to the rigid head.

5. A casting machine comprising an arm, means supporting said arm for rotation about an axis spaced from an end thereof, a motor, means connecting the arm to said motor to be rotated thereby, a head rigid with said arm adjacent said end thereof, a follower head adjustably carried by said arm, said heads having a plurality of aligned recesses of various sizes therein for the reception of the ends of the mold, means for adjusting the position of said follower head in respect to the rigid head, and means carried by said rigid head for introducing self-hardening material to said mold during rotation of the arm.

6. A casting machine comprising a hollow arm, means supporting said arm for rotation about an axis spaced from an end thereof, a motor, means connecting the arm to said motor to be rotated thereby, a head rigid with said arm adjacent said end thereof, arod slidably received within said arm and extending beyond saidv head, a follower head rigid with said rod, said heads having alinged recesses therein for the reception of the ends of a mold, means for introducing molten inaterial into said mold during rotation of said arm, a rod revoluble inside said arm and threadedly engaged with said slidable rod, and a. head at the other end of said arm and ri id with said threaded rod.

A casting machine comprising a hollow arm, means supporting said arm for rotation about an axis spaced from an end thereof, a motor, means connecting the arm to said motor to be rotated thereby, a head rigid with said arm adjacent said end thereof, a rod slidably received within said arm and extending beyond said head, a'n follower head rigid with said rod, said heads having aligned recesses therein for the reception of the ends of a mold, means holding saidvrod against rotation within the arm, means for introducing molten material into said mold during rotation of said arm, a rod revoluble inside said arm and threadedly engagedwith said slidable rod, and a head at the other end of said arm and rigid with said threaded rod.

8. A casting machine comprising a hollow arm, means supporting said arm for rotation about an axis spaced from an end thereof, a motor,` means connecting the arm to said motor to be rotated thereby, a head rigid with said arm adjacent said end thereof, a rod slidably received within said arm and extending beyond said head, a follower head i rigid with said rod, said heads having alinged recesses therein for the reception of the ends of a mold, means for introducing molten materia-l into said mold during rotation of said arm, and a head at the other end of the arm connected to said rod to eect sliding of the rod within the arm thereby.

9. A casting machine comprising a mold having a gate therein, revoluble means sup porting said mold for rotation about an axis spaced from the mold, theaxis of said gate being disposed radially in respect to the axis of rotation, means for introducing molten material into said gate during rotation of said supporting means, and means connected to said supporting means to e'ect rotation thereof at a uniform rate throughout a prolonged period of time.

10. A casting machine comprising a mold having a gate therein, revoluble means supporting said mold lfor rotation about an axis spaced from the mold, the axis of said gate extending outwards from the axis of rotation, means for introducing molten material into said gate during rotation of said supporting means, a motor, means coupling said motor to said supporting means to effect rotation thereof, said coupling means being inoperative until said motor has attained its maximum speed.

11. A casting machine comprising a mold having a gate therein, revoluble means supporting said mold for rotation about an axis spaced from the mold, the axis of said gate being disposed radially in respect to the axis of rotation, means for introducing molten material into said gate during rotation` of said supporting means, and means for suddenly imparting rotation to said arm and maintaining said rotation at a speed as great as the initial speed of saidarm.

12. A casting machine comprising a mold, revoluble means supporting said mold for rotation about an axis spaced from said mold, means for introducing molten material into said mold by centrifugal force during rotation of said supporting means, a motor having a shaft disposed with its axis coincident with the axis of rotation of said supporting means, and a flexible connecting member secured to said shaft and to said supporting means to impart rotation to the supporting means after the slack of said flexible member has been taken up.

13. A casting machine comprising a mold, revoluble means supporting said mold for rotation about an axis spaced from said mold, means for introducing molten material into said mold by centrifugal force during rotation ofsaid supporting means, a motor having a shaft disposed with one end thereof adjacent said supporting means and with its axis coincident with the axis of rotation of the supporting means, and a iexible connecting member secured to said supporting means and to said shaft to rotate the supporting means after the slack of the flexible member has been Wou-nd upon the shaft.

14. A casting machine comprising a base, an arm revolubly mounted thereon, an electrically heated crucible carried by said arm and s aced from the axis of revolution thereo a mold carried by said arm beyond the Crucible from said axis, a pair of insulating heads mounted in axial coincidence with the axis of rotation of said arm, one o said heads being rigid with the arm and the other with the base, contacts carried by each head adapted to engage those of the other head, conductors connecting the contacts on the movable head with the Crucible, and means for supplying electrical energy to the contacts on the fixed head.

15. A casting machine comprising a base, an arm revoiubly mounted thereon, an electrically heated Crucible carried by said arm and spaced from the 'axis of revolution thereof, a thermo-couple associated with said Crucible, a mold carried by said arm beyond the Crucible rom said axis, a pair of insulating heads mounted in axial coincidence With the axis of rotation of said arm', one of said heads being rigid with the arm and the other with the base, pairs of contacts carried by each head, those of one head being adapted to engage those of the other head, conductors connecting said crucible with certain of the contacts of the movable head, means for,

supplying electrical energy to the associated contacts on the stationary head, conductors connecting the other contacts on the movable head with the thermo-couple, and means connected to the associated contacts on the stao tionary head for indicating the current generated in the thermo-couple.

In testimony whereof I have signed my name to this speciication.

ROBERT P. FRlST, JR. 

